The proposed studies seek to study the interactions of microtubules with dynein or with mitotic microtubule organizing centers in vitro in order to understand how microtubules function in vivo. Experiments will be undertaken to determine if microtubules crossbridged by dynein can slide relative to each other upon addition of ATP or if isolated pigment granules or dynein coated beads can move along microtubules in vitro. The precise location of cytoplasmic dynein in the mitotic apparatus as well as the ability of this dynein to bind, crossbridge and induce ATP dependent sliding between microtubules will be assessed. The polarity of assembly and the structural polarity of microtubules assembled from mitotic microtubule organizing centers will also be examined. Microtubules emanating from kinetochores or centrosomes will be decorated with dynein and subsequently elongated in tubulin. Newly assembled regions of the microtubules should be devoid of dynein. Moreover, the ability of chromosomes to initiate the assembly of microtubules in vitro having the same polarity as do the kinetochore microtubules in vivo will be examined. Finally, it will be determined if dynein binds cooperatively along the B subfiber of outerdoublets, a process which may be responsible for wave propagation along the axoneme. Results of these studies will contribute to an understanding of th mechanism by which movements occur in association with microtubules.